Ma huang, an extract from the ephedra species of plants,...

Ma huang, an extract from the ephedra species of plants, contains ephedrine. The Chinese have used this herb more than 5000 years to treat asthma. More recently the substance has been used in diet pills that can be purchased over the counter in herbal medicine shops. However, very serious concerns have been raised regarding these pills following reports of serious heart problems with their use. (a) Write the molecular formula for ephedrine, draw its structural formula, and calculate its molar mass. (b) What is the weight percent of carbon in ephedrine? (c) Calculate the amount (moles) of ephedrine in a $0.125-\mathrm{g}$ sample. (d) How many molecules of ephedrine are there in $0.125 \mathrm{g} ?$ How many C atoms? (FIGURE CANNOT COPY)

Ma huang, an extract from the ephedra species of plants, contains ephedrine. The Chinese have used this herb more than 5000 years to treat asthma. More recently the substance has been used in diet pills that can be purchased over the counter in herbal medicine shops. However, very serious concerns have been raised regarding these pills following reports of serious heart problems with their use.
(a) Write the molecular formula for ephedrine, draw its structural formula, and calculate its molar mass.
(b) What is the weight percent of carbon in ephedrine?
(c) Calculate the amount (moles) of ephedrine in a $0.125-\mathrm{g}$ sample.
(d) How many molecules of ephedrine are there in
$0.125 \mathrm{g} ?$ How many C atoms?
(FIGURE CANNOT COPY)

Key Concepts

Molecular Formula

The molecular formula represents the number and types of atoms present in a molecule, showing the basic composition of the compound without detailing how those atoms are arranged. It is crucial in chemistry as it provides the starting point for further analyses such as molar mass calculation and the study of chemical reactions.

Structural Formula

The structural formula illustrates how the atoms in a molecule are bonded to each other, including the arrangement of bonds and any functional groups. This representation is essential for understanding the compound's geometry, reactivity, and the biological interactions, especially in the context of organic compounds like ephedrine.

Molar Mass Calculation

Molar mass is the mass of one mole of a substance, calculated by summing the atomic masses of all atoms in its molecular formula. This concept is important because it allows chemists to convert between the number of moles and the mass of a substance, a fundamental process in stoichiometric calculations.

Weight Percent Composition

Weight percent composition refers to the percentage of each element's mass within a compound relative to the total molecular mass. This calculation is important for determining the proportion of each element in a compound, which is useful in material composition analysis and quality control in chemical manufacturing.

Stoichiometry

Stoichiometry involves the quantitative relationships between reactants and products in chemical reactions. It uses measurements like mass, moles, and molar mass to determine the proportional amounts needed or produced, which is critical for both lab work and industrial applications.

Avogadro's Number

Avogadro's number, approximately 6.022 x 10^23, is the number of atoms, ions, or molecules in one mole of a substance. It bridges the gap between the microscopic scale of atoms and molecules and the macroscopic scale of grams and liters, enabling chemists to count particles by weighing a substance.

Transcript

00:01 In this problem, we are given the 3d structure of ephedrine, which is represented by the ball and stick model.

00:14 First, we need to determine out of the ball and stick model the molecular formula.

00:24 So you have to count the number of each type of atoms, the number of carbon, the number of hydrogen, and the number of nitrogen.

00:33 And also the number of oxygen.

00:36 So there are four carbons represented in the structure.

00:40 When you count that, you get that you have 10 carbons, 15 hydrogens, one nitrogen, and one oxygen.

00:54 And this is the molecular formula of effigrine.

01:02 Next, we have to draw the structure of effigris.

01:09 The structure formula of effigrine in other words we have to convert the 3d structure in a 2d or planar structure so the first thing we see is a bengen group or a bengen ring which is drawn like this okay and then we have five hydrogens coming out of the bengen ring in the bengen ring each vertex here is a carbon okay it's an atom of carbon each one of this vertex here is an atom of carbon this carbon and each of this carbon is bound to a hydrogen this carbon however is not bound to a hydrogen but rather to another carbon and this carbon is bound to an oxygen which is further bound to a hydrogen this carbon is also bound to another carbon and another hydrogen here.

02:35 This carbon is bound to another carbon, which is bound to three hydrogens.

02:49 This carbon is bound to another hydrogen here, a nitrogen, and this nitrogen is bound to a hydrogen and another methyl group, which is a carbon, and three, bound to three, and three hydrogens.

03:15 So let's just verify that this drawing coincide with the molecular formula.

03:23 So let's count the number of carbon.

03:25 One, two, three, four, five, six, which makes, which made the benzene green.

03:31 Seven, eight, nine, ten carbon.

03:36 Now hydrogens.

03:38 One, two, three, four, five, six, seven, 8, 9, 10, 11, 12, 13, 14, 15, 15, 15 hydrogen.

03:50 One nitrogen is here, when oxygen is here.

03:55 So we're good.

03:57 Next, we have to calculate the molar mass of this compound.

04:04 The molar mass is the sum of all the atomic masses represented by the atoms here.

04:12 So for carbon, we have 10 carbons and each carbon weighs 12 grams.

04:22 That's the atomic mass of carbon.

04:23 Carbon is weight 12 grams per mole and we have 10 of those, 10 carbons...

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